ALSA: bt87x: Proper endian notations

The RISC data in bt87x is in little-endian, hence we should define it
with __le32 properly.

Spotted by sparse, a warning like:
  sound/pci/bt87x.c:240:17: warning: incorrect type in assignment (different base types)
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/bt87x.c

@@ -228,14 +228,14 @@ static int snd_bt87x_create_risc(struct snd_bt87x *chip, struct snd_pcm_substrea
 			       	 unsigned int periods, unsigned int period_bytes)
 {
 	unsigned int i, offset;
-	u32 *risc;
+	__le32 *risc;
 
 	if (chip->dma_risc.area == NULL) {
 		if (snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, snd_dma_pci_data(chip->pci),
 					PAGE_ALIGN(MAX_RISC_SIZE), &chip->dma_risc) < 0)
 			return -ENOMEM;
 	}
-	risc = (u32 *)chip->dma_risc.area;
+	risc = (__le32 *)chip->dma_risc.area;
 	offset = 0;
 	*risc++ = cpu_to_le32(RISC_SYNC | RISC_SYNC_FM1);
 	*risc++ = cpu_to_le32(0);